Over the years, it has become very convenient to address Wide Area Network (WAN) performance issues with Citrix terminal server. Actually it is indeed an effective solution to accelerate access to normal applications (Web and non-Web); furthermore it is easy to setup and deploy. However when it comes to accelerating complex Web applications such as SAP CRM and WebDynpro applications, it may not be the case.
In the last few years I worked with a few customers whose global users suffered from WAN performance issues. As a quick-and-easy remedy, they implemented a Citrix terminal server for their remote users. Soon after a good number of users were working via the Citrix server, their screens started to hang. A quick analysis revealed that the CPUs on the Citrix box were fully occupied by the Web Browsers accessing SAP applications, such as CRM, custom WebDynpro Java applications, etc.
On the other hand, if we deploy a WAN acceleration solution such as SAP NetWeaver Accelerated Application Delivery (AccAD), the CPU load (by web browsers) will be evenly distributed to many end users’ workstations, which makes it a more scalable solution. By the way, for remote users who can’t even access Citrix terminal server with acceptable performance due to high network latency and low network throughput, AccAD would still provide a decent user experience for them.
The underlying problem is, with the current Web technologies, web pages often become very heavy for web browsers to render and execute, especially when you implement complex business transactions with rich user interface in those web pages. Due to the nature of SAP business applications, many of them fall into this case. Therefore in a SAP-centric scenario, it makes sense to choose a WAN acceleration solution (such as AccAD) to accelerate WAN traffic over Citrix terminal service.
1) Normally hardware acceleration for UI can only happen when the user is connected to the console session of Windows, not when they are logged on to terminal sessions* (*this may change in the future with Microsoft RemoteFX technology).
In a word, if you are trying to accelerate Web access to your SAP systems over WAN, it is more advisable to consider a WAN acceleration solution, such as SAP AccAD, especially if you have a large number of remote users. The high CPU consumption on the Citrix terminal server box would defeat the purpose of setting it up.